The present disclosure generally relates to systems and methods of optical computing and, more specifically, to improved imaging systems for an optical train in optical computing devices.
Optical computing devices, also commonly referred to as “opticoanalytical devices,” can be used to analyze and monitor a sample substance in real time. Such optical computing devices will often employ a light source that emits electromagnetic radiation that either reflects from or is transmitted through the sample and optically interacts with an optical processing element to determine quantitative and/or qualitative values of one or more physical or chemical properties of the substance being analyzed. The optical processing element may be, for example, an integrated computational element (ICE). One type of an ICE is an optical thin film interference device, also known as a multivariate optical element (MOE). Each ICE can be designed to operate over a continuum of wavelengths in the electromagnetic spectrum from the UV to mid-infrared (MIR) ranges, or any sub-set of that region. Electromagnetic radiation that optically interacts with the sample substance is changed and processed by the ICE so as to be measured by a detector. The output of the detector is then correlated to a physical or chemical property of the substance being monitored.
Some optical computing devices optically interact with the sample substance via a sampling window that separates the internal components of the optical computing device from the sample substance. The light that impinges upon the sample substance via the sampling window is dispersed by the substance and reflected back through the sampling window so that it can be collected and quantified by a detector associated with the optical computing device. The sensitivity and accuracy of some optical computing devices, however, can be limited by stray light that emanates primarily from the sampling window interface (both front and back surfaces). Such stray light can dilute, warp, or otherwise mask the light of interest that is reflected from the sample substance. As a result, light reflected off the sampling window and sensed by the detector can inaccurately detect the information of interest.